Electrically powered artificial lighting has become ubiquitous in modern society. Electrical lighting devices are commonly deployed, for example, in homes, commercial buildings and other enterprise establishments, as well as in various outdoor settings.
Lighting devices take many forms, for example, ranging from aesthetically appealing residential use luminaires to ruggedized industrial lighting devices configured according to the environment in which the luminaire is located. A primary function of a lighting device is to provide general illumination that complies with governmental regulations and industry standards applicable to the environment in which the lighting device is installed.
Examples of other uses of lighting in combination with display technologies includes various configurations of signage that include light sources as backlighting that are positioned behind a design feature such a diffuser or screen with an image or wording. Examples of such backlit signage includes advertising signs, door exit signs and other examples of signage that would benefit from backlighting. Some of the signs may be controllable to change wording or an image presented on the display device of the sign. In some instances of advertising signage, a transparent display can be used to provide advertising without obstructing a view of either the interior of a store when viewed from the exterior or vice versa, as well as providing an easily changeable design. However, backlit signage without additional lighting is not typically configured to provide general illumination that complies with governmental regulations and industry standards applicable to the environment in which the signage is installed.
There have been more recent proposals to develop transparent displays using organic light emitting devices (OLEDs) for purposes of providing augmented reality experiences, and to provide smart windows, doors or even furniture. However, due to the construction of these transparent displays, the optical transmissivity of some of these displays is only 45% with a pixel size of 0.63 millimeters. This lack of transmissivity hinders full utilization of the transparent attributes of the transparent display for purposes other than the augmented reality experience or as smart windows.
Although more recent transparent display proposals provide a greater transmissivity than previous attempts, the transmissivity of the transparent display device may be further improved to provide greater transmissivity.
Recent developments in the use of OLED devices have enabled color tunable light sources. In an example, the Fraunhofer Institute has also shown that a tunable OLED device that emits a range of different colors may be formed by arranging different color light emitting OLEDs over one another. The OLED described by the Fraunhofer Institute is used in a lighting device to provide tunable light ranging from a warm yellow color to a cooler blue color.
Furthermore, there have been proposals to use displays or display-like devices mounted in or on the ceiling to provide variable lighting. The Fraunhofer Institute, for example, has demonstrated a lighting system using luminous tiles, each having a matrix of red (R) LEDs, green (G), blue (B) LEDs and white (W) LEDs as well as a diffuser film to process light from the various LEDs. The LEDs of the system were driven to simulate or mimic the effects of clouds moving across the sky. Although use of displays with a lighting device allows for variations in appearance that some may find pleasing, the displays or display-like devices are optimized for image output and do not provide particularly good illumination for general lighting applications.
Opportunities exist to improve upon the transmissivity of transparent OLED display devices for various applications, including for use as (or as part of) a lighting device.